This can be very helpful when exploring the outer reaches of the Thames by bicycle, and all you have to do is show up at the Essex or Kent Control Point and on a weekend you will soon be picked up. On a weekday pickups are staggered so that they sometimes only take place in certain hours of the day so it's worth contacting the operators in advance to ensure you don't have to wait an hour. Those approaching from the Kent side should note there is a telephone hidden around the corner behind the Control Point to call for a lift, which again will help reduce the wait. There probably will be at least some waiting whatever happens so be sure to factor that into your ride.
For more, visit the Highways Agency website.